Dielectric materials in high-density circuits appear as capacitors in dynamic random access memory (DRAM) applications, gate dielectrics in transistors and as decoupling capacitors. The dielectric in these structures is typically silicon dioxide, i.e., SiO2, silicon nitride, i.e., Si3N4, or any combinations thereof. These dielectrics have a relative dielectric constant, i.e., k, of about 8.0 or below.
In the case of capacitors, the main focus is on the development of high capacitance/area devices with low series resistance of the top and bottom electrodes for high frequency responses. High capacitance/area devices require the use of dielectric materials that are thin (on the order of about 200 Å or less). The use of conventional, thin low-k dielectrics in today's devices is undesirable since such materials lead to leaky devices. Moreover, as conventional chemical vapor deposited and thermal low-k dielectrics become thinner, it is increasingly becoming more difficult to meet reliability limitations. Therefore, alternatives to conventional, thin low-k dielectrics that do not exhibit the above-mentioned leakage problem are continually being sought in the semiconductor industry.
In the case of FEOL capacitors such as poly-poly capacitors and MIS capacitors, the integration of high-k dielectrics (k of greater than about 8) into the capacitor structure is difficult because of the high-deposition temperatures (typically greater than 600° C.) used in depositing the high-k dielectric onto the silicon-containing electrode. At such high-deposition temperatures, interfacial layers form in the silicon layer which may degrade device performance. In addition, grain boundary leakage paths and lowered barrier heights may result which could lead to devices that are highly unreliable.
In view of the above drawbacks in the prior art, there is a need for fabricating FEOL capacitors that have a high capacitance/area with low series resistance of the top and bottom electrodes. Moreover, there is a need for developing FEOL capacitors that contain a thin high-k dielectric which has improved reliability, leakage currents and stability as compared with prior art FEOL capacitors.